This invention relates generally to video production, photographic image processing, and computer graphics design, and, more particularly, to a multi-format video production system capable of professional quality editing and manipulation of images intended for television and other applications, including HDTV programs.
As the number of television channels available through various program delivery methods (cable TV, home video, broadcast, etc.) continues to proliferate, the demand for programming, particularly high-quality HDTV-format programming, presents special challenges, both technical and financial, to program producers. While the price of professional editing and image manipulation equipment continues to increase, due to the high cost of research and development and other factors, general-purpose hardware, including personal computers, can produce remarkable effects at a cost well within the reach of non-professionals, even novices. As a result, the distinction between these two classifications of equipment has become less well defined.
The parent to this application, for example, describes a video production system which integrates equipment supplied by various manufacturers, enabling a consumer to produce and edit video material using an enhanced personal computer. An adapter unit interfaced to each camera in use with the system connects to a camera interface module, and each camera interface module, in turn, feeds a computer interface unit. These computer interface units communicate with a personal computer over a standard interconnect, allowing an operator to control the various cameras while viewing individual video programs which appear in separate xe2x80x9cwindowsxe2x80x9d on the computer monitor.
This related invention solves many of the problems associated with combining commercially available hardware to create an economical personal-computer-based system capable of very high quality audio/video production. However, the variety of available and planned program standards and delivery methods places further demands on video production equipment, including the editing and manipulation of images not only from a variety of sources, but in differing pixel formats, frame rates, and so forth. Although general-purpose PC-based equipment may never allow professional-style rendering of images at full resolution in real-time, each new generation of microprocessors enables progressively faster, higher-resolution applications. In addition, as the price of memory circuits and other data storage hardware continues to fall, the capacity of such devices has risen dramatically, thereby improving the prospects for enhancing PC-based image manipulation systems for such applications.
In terms of dedicated equipment, attention has traditionally focused on the development of two kinds of professional image-manipulation systems: those intended for the highest quality levels to support film effects, and those intended for television broadcast to provide xe2x80x9cfull 35 mm theatrical film quality,xe2x80x9d within the realities and economics of present broadcasting systems. Conventional thinking holds that 35 mm theatrical film quality is equivalent to 1200 or more lines of resolution, whereas camera negatives present 2500 or more lines. As a result, image formats under consideration have been directed towards video systems having 2500 or more scan lines for high-level production (such as the Kodak xe2x80x9cElectronic Intermediatexe2x80x9d system described by Hunt et al.), with hierarchies of production, HDTV broadcast, and NTSC and PAL compatible standards which are derived by down-converting these formats. Several techniques have been described, including those of Bretyl (xe2x80x9c3xc3x97NTSC xe2x80x98Leapfrogxe2x80x99 Production Standard for HDTVxe2x80x9d, SMPTE Journal, March 1989), Demos (xe2x80x9cAn Example Hierarchy of Formats for HDTVxe2x80x9d, SMPTE Journal, September 1992), and Lim (xe2x80x9cA Proposal for an HDTV/ATV Standard with Multiple Transmission Formatsxe2x80x9d, SMPTE Journal, August 1993). Most proposals employ progressive scanning, although interlace is considered an acceptable alternative as part of an evolutionary process. In particular, Demos addresses the important issue of compatibility to computer-graphics-compatible formats, although he begins with an 1152-line format, and only considers progressive scanning. And, as pointed out by Thorpe et al., progressive scanning also has drawbacks, and as shown by Kaiser et al. (xe2x80x9cResolution Requirements for HDTV Based Upon the Performance of 35 mm Motion-Picture Films for Theatrical Viewingxe2x80x9d, SMPTE Journal, June 1985), even 35 mm theatrical film quality is a misnomer since the realities of mechanical projection systems restrict the typical screen display to less than 700 TV lines/picture height.
Current technology directions in computers and image processing should allow production equipment based upon fewer than 1200 scan lines, with picture expansions to create a hierarchy of upward-converted formats for theatrical projection, film effects, and film recording. In addition general-purpose hardware enhancements should be capable of addressing the economic aspects of production, a subject not considered in detail by any of the available references.
The present invention takes advantage of general-purpose hardware where possible to provide an economical multi-format video production system. In the preferred embodiment, specialized graphics processing capabilities are included in a high-performance personal computer or workstation, enabling the user to edit and manipulate an input video program and produce an output version of the program in a final format which may have a different frame rate, pixel dimensions, or both. An internal production format is chosen which provides the greatest compatibility with existing and planned formats associated with standard and widescreen television, high-definition television, and film. For compatibility with film, the frame rate of the internal production format is preferably 24 fps. Images are re-sized by the system to larger or smaller dimensions so as to fill the particular needs of individual applications, and frame rates are adapted by inter-frame interpolation or by traditional schemes, including xe2x80x9c3:2 pull-downxe2x80x9d for 24-to-30 fps conversions, or by manipulating the frame rate itself for 24 to 25 fps for a PAL-compatible display. The enhancement to a general-purpose platform preferably takes the form of a graphics processor connected to receive a video signal in an input format. The processor comprises a plurality of interface units, including a standard/widescreen interface unit operative to convert the video program in the input format into an output signal representative of a standard/widescreen formatted image, and output the signal to an attached display device. A high-definition television interface unit is operative to convert the video program in the input format into an output signal representative of an HDTV-formatted image, and output the signal to the display device. A centralized controller in operative communication with the video program input, the graphics processor, and an operator interface, enables commands entered by an operator to cause the graphics processor to perform one or more of the conversions using the television interfaces. The present invention thus encourages production at relatively low pixel dimensions to make use of lower-cost general-purpose hardware and to maintain high signal-to-noise, then subsequently expands the result into a higher-format final program. This is in contrast to competing approaches, which recommend operating at higher resolution, then down-sizing, if necessary, to less expensive formats which has led to the high-cost, dedicated hardware, the need for which the present invention seeks to eliminate.